1. Technical Field
The present invention relates to an adjustable orthosis for stretching tissue in the human body. In particular, the present invention relates to an adjustable orthosis which distracts a joint during extension of the joint.
2. Description of the Prior Art
In circumstances in which full extension of a joint in a human limb is not available, such as after surgery or trauma, the joint stiffens and loses its full range of motion. Various devices have been designed to flex and extend the joint to regain range of motion.
U.S. Pat. No. 4,612,919 shows an adjustable limb support for adjustably orienting the forearm and upper arm of a human patient in a variety of angular relationship to therapeutically treat the contracted muscles in the patient's arm.
U.S. Pat. No. 4,848,326 shows a knee contracture correction device for straightening a contracted knee.
U.S. Pat. No. 4,538,600 shows an adjustable splint assembly with a lower strut and an upper strut pivotably connected to the lower strut. An internal spring applies a force at the pivot point to align the upper and lower struts to straighten the limb to which the splint is attached. A similar device is also shown in U.S. Pat. No. 4,508,111. Similar devices are in use and are sold under the trademark DYNASPLINT by Dynasplint Systems, Inc.
U.S. Pat. No. 4,665,905 shows a dynamic elbow and knee extension device with a centrally positioned compression spring.
It is also known in the art to put a rigid element including a turnbuckle, on the inside angle of a joint, between two cuffs attached to limb segments and use the turnbuckle to vary the length of the rigid element to pull and push the limb segments relative to each other. It has been found that this device does not work very well in practice because it is cumbersome and difficult to obtain relatively full extension or flexion at the extremes of motion.
When the joint stiffens, joint tissues such as ligaments, tendons, and muscles around the bones also become compressed and less flexible. Therefore, joint therapy should not merely seek to improve the range of motion of the joint (that is, the angle through which the joint can be flexed and extended). Rather, joint therapy should be also directed to obtaining distraction of the joint. "Distraction" is defined by one dictionary as "Separation of the surfaces of a joint by extension without injury or dislocation of the parts." (Taber's Cyclopedic Medical Dictionary, 16th Edition, 1989, page 521), and involves stretching the joint capsule, soft tissue, ligaments, and tendons. Further, it is also desirable to distract the joint without increasing the joint reactive force.
None of the above-identified prior art devices, and none of the devices in use at the present time, functions to distract the joint upon extension of the joint. None allows the patient to provide the needed therapy by himself, without the assistance of a therapist who manually stretches the joint. None allows the patient to control the therapy process in a self-directed manner. Accordingly, it is desirable to provide a device which not only enhances the range of motion of the joint but also distracts the joint and stretches soft tissue.